Nice design, but not exactly new. The EU has had regulations for the design and construction EPACs (electrically power assisted cycles) since 2009.

There need to be some rules to distinguish them from more powerful electric vehicles requiring mandatory tax, insurance, driving tests, etc.

Current UK law is a bit more restrictive than the EU regulations and is summarized here:https://www.gov.uk/electric-bike-rules The EU regulations permit slightly higher motor power, and higher max speed with power assistance.

The generic name over here is "pedelecs". See google...

Some studies have found there are safety downsides. For example, motorists may wrongly predict how an electrically assisted bike will be ridden (speed traveling up hills, acceleration, etc), compared with a conventional bike.